用LINQtoSQL创建Web应用系统（三）
来源:网络 作者:佚名 点击:
次时间:2017-11-17 03:45
[摘要] 使用LINQ实现数据访问层 数据访问层包含与Data Linq交互的代码，它使用集成语言查询来访问Data Linq层。下图2.1 展示了数据访问层的细节。基本上，它包括了所有与上层交互的方法，并完成与数据
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使用LINQ实现数据访问层
数据访问层包含与Data Linq交互的代码，它使用集成语言查询来访问Data Linq层。下图2.1 展示了数据访问层的细节。基本上，它包括了所有与上层交互的方法，并完成与数据库相关的操作。
图2.1：数据访问层-详细视图
在示例程序中，数据访问层包含了一个简单的组件DALCustomer，相关代码如下（http://www.EntLib.com 开源小组注： 这里相关的示例代码采用C#，原文为VB代码）：
代码片段1.1：数据访问层
public class DALCustomer
{
private DBLinqDataContext objDataContext = new DBLinqDataContext();
public Table<Customer> SelectRecordAll()
{
try
{
return objDataContext.Customers;
}
catch(Exception ex)
{
throw ex;
}
}
public Customer SelectRecordByID(string customerID)
{
try
{
return (from cust in objDataContext.Customers
where cust.CustomerID == customerID
select cust).Single();
}
catch (Exception ex)
{
throw ex;
}
}
public List<Customer> SelectRecordByIDListable(string customerID)
{
List<Customer> localTable;
try
{
localTable = (from cust in objDataContext.Customers
where cust.CustomerID == customerID
select cust).ToList();
return localTable;
}
catch (Exception ex)
{
throw ex;
}
}
public string InsertRecord(Customer localTable)
{
try
{
objDataContext.Customers.InsertOnSubmit(localTable);
objDataContext.SubmitChanges();
return localTable.CustomerID;
}
catch (Exception ex)
{
throw ex;
}
}
public void UpdateRecord(Customer localTable)
{
try
{
objDataContext.Customers.Attach(localTable);
objDataContext.Refresh(RefreshMode.KeepCurrentValues, localTable);
objDataContext.SubmitChanges(ConflictMode.ContinueOnConflict);
}
catch (Exception ex)
{
throw ex;
}
}
public void DeleteRecord(string customerID)
{
try
{
objDataContext.Customers.DeleteOnSubmit((from cust in objDataContext.Customers
where cust.CustomerID==customerID
select cust).Single());
objDataContext.SubmitChanges();
}
catch(Exception ex)
{
throw ex;
}
}
public Table<Order> SelectAllOrder()
{
try
{
return objDataContext.Orders;
}
catch (Exception ex)
{
throw ex;
}
}
public Table<Order_Detail> SelectAllOrderDetail()
{
try
{
return objDataContext.Order_Details;
}
catch (Exception ex)
{
throw ex;
}
}
} |
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